API updates

- Move all generic API classes definitions to the rest_api.generics
module.
- Update API status code on insufficient access for the apps:
indexes, parsing, documents, metadata, ocr, permission,
user management.
- Update API tests.

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/sources/api_views.py

@@ -3,9 +3,10 @@ from __future__ import unicode_literals
 from django.http import HttpResponse
 from django.shortcuts import get_object_or_404
 
-from rest_framework import generics
 from rest_framework.response import Response
 
+from mayan.apps.rest_api import generics
+
 from .literals import STAGING_FILE_IMAGE_TASK_TIMEOUT
 from .models import StagingFolderSource
 from .serializers import StagingFolderFileSerializer, StagingFolderSerializer